On Fri, 14 Aug 1998, Miller,Eric wrote:
> A new public version of the W3C RDF Schema draft specification is now
> available.
>
> http://www.w3.org/TR/WD-RDF-schema
>
> RDF Schemas are used to declare vocabularies, the sets of semantics
> defined by a particular resource description community. [snip]
Just to followup Eric's announcement with some side notes and excerpts
to followup the "Is RDF the Warwick Framework's representative on
earth?" comments earlier this week.
This new version of the draft now includes some brief allusions to the
Resource Description Framework's intellectual heritage in the Warwick
Framework.
A handful of excerpts below for those uninterested in the
technical nitty gritty in the document itself.
In passing, the Dublin Core's theoretical underpinnings in the Warwick
Framework leave it, IMHO, well positions to respond to critiques such as
<URI:http://www.dlib.org/dlib/july98/rust/07rust.html> which argue
explicitly for a monolithic one-size-fits all resource description
vocabulary. (see for example the claim that DC endorses 'defeatism of
the highest order' when we argue that "no single data element set
whether limited or unlimited would satisfy the widely divergent and
highly specific needs of the various stakeholders").
[cue separate thread!].
Excerpts from the RDF Schemas doc follow.
>From http://www.w3.org/TR/WD-rdf-schema/ intro:
[...]
RDF and the RDF Schema language were also based on metadata research in
the the Digital Library community. In
particular, RDF adopts a modular approach to metadata along the lines of
the Warwick Framework [WF]. RDF represents
an evolution of the Warwick Framework model in that the Warwick
Framework allowed each metadata vocabulary to be
represented in a different syntax. Within RDF, all vocabularies are
expressed within a single well defined model and
syntax. This allows for a finer grained mixing of machine-processable
vocabularies, and addresses the need [EXTWEB] to
create metadata in which statements can draw upon multiple vocabularies
that are managed in a decentralised fashion by various
communities of expertise
from section 3 (Constraints)
[...]
RDF schemas can express constraints that relate vocabulary items from
multiple independently developed schemas. Since
URI references are used to identify classes and property types, it is
possible to create new property types whose domain or
range is constrained to be a class defined in another namespace.
Also, Example 2 in the appendix gives a (fictional!) example of a schema
for describing internet search services which might, Warwick Framework
style, call upon multiple vocabularies, DC and other, rather than
attempt to do everything in one monolithic namespace:
[Please note this is an EXAMPLE schema only]
In this example we sketch an outline of an RDF vocabulary for use with
searchable Internet services. SearchQuery is a
declared to be a class. Every SearchQuery must have both a queryString
whose value is a String and a queryService
whose value is a SearchService. A SearchService is a subclass of
InternetService (which is defined elsewhere). A
SearchQuery has some number of results (whose value is SearchResult).
Each SearchResult has a title (value is a string),
a rating (value is between 0 and 1) and of course, the page itself.
The modularity of RDF allows other vocabularies to be combined with
simple schemas such as this to characterise more
fully the properties of networked resources. For example, Dublin Core or
a library-based classification vocabulary might be
used to describe the subject coverage or collections-level properties
for each SearchService, while an independently
managed "search protocols" vocabulary could be used to describe
connection details for (say) LDAP, WHOIS++ or Z39.50
search interfaces offered by the service. By allowing the creation of
statements which draw upon specialised schemas from
various domains, RDF makes it possible for communities of expertise to
contribute to a decentralised web of machine-readable
vocabularies.
Comments c/o mailto:[log in to unmask] or on meta2
(spiritual home of the Warwick Framwork?) as appropriate.
Dan
--
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Institute for Learning and Research Technology http://www.ilrt.bris.ac.uk/
University of Bristol, Bristol BS8 1TN, UK. tel: +44(0)117 9288478
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